1. Field of the Invention
The present invention relates to printed circuit board assemblies and methods for assembling electronic components into multi-layer assemblies. More particularly, the present invention relates to RF power amplifier circuit board assemblies and related methods of assembly.
2. Description of the Prior Art and Related Background Information
In high power electronics assemblies generating a relatively high amount of heat, it is typically necessary to attach a printed circuit board (PCB) containing electronic components to a metal substrate provided as a heat sink. RF power amplifiers are an example of such electronics module assemblies that incorporate heat dissipation means by design. The metal substrate for an electronics module may further be needed for grounding and electromagnetic interference (EMI) shielding. The use of nonconductive adhesives is a particular cost effective method of attaching a two sided printed circuit board to a metal substrate. The drawback to this approach is that there is no intimate metal-to-metal contact between the metal substrate and the metalized backside of the PCB. To achieve electrical and thermal contact at critical locations of this interface, it is desirable to use surface applied solder paste that is applied to a top surface of the PCB. However, trapped air and gases created during the solder reflow process create backpressure and prevent the molten solder from flowing.
Accordingly, a need presently exists for a way to use cost effective nonconductive adhesive bonding and also provide effective electrical and thermal coupling to the substrate using surface applied solder reflow techniques.